A novel heterocyclic and plank-shape diamine monomer, 2,6-(4,4′-diaminodiphenyl) benzo[1,2-d:5,4-d'] bisoxazole (PBOA), was successfully synthesized from readily available compounds of 4,6-diaminoresorcinol dihydrochloride (DAR) and p-aminobenzoic acid (PABA). A series of poly(benzobisoxazole-co-imide) (PBOI) fibers based on 3,3′,4,4′-biphenyltetracarboxylic anhydride (BPDA), 4,4′-diaminodiphenyl ether (ODA) and PBOA were fabricated via a two-step wet-spinning method. PBOA was characterized in detail, and the effect of the monomer in the polymer backbones on the fibers' microstructure and properties were described. 2D wide-angle X-ray diffraction indicated that the incorporated PBOA in the BPDA-ODA polyimide backbone is beneficial for forming well-defined crystalline regions in the resulted fibers during the thermal stretching process and significantly improving the crystallinity and crystal orientation of the drawn PBOI fibers. Small-angle X-ray scattering patterns of the drawn PBOI fibers suggested the presence of typical periodic lamellar crystal in the fibers. It is shown that increasing PBOA contents will result in higher values of the long period (L) and the lamellar thickness (l_C). Maximum improvements of 153% in tensile strength and 282% in modulus were achieved when increasing the molar content of PBOA in the mixed diamine from 10 mol% to 50 mol%. Correspondingly, the temperature at the maximum degradation rate (T_d-max) and glass transition temperature (T_g) of resulted PBOI fibers in nitrogen increased by 28 and 30 °C, respectively, making these novel polymeric fibers as good reinforcements in fabricating advanced composites.

新型的杂环和板状二胺单体2,6-（4,4'-二氨基二苯基）苯并[1,2-d：5,4-d']双恶唑（PBOA）已成功地从容易获得的4,6-二氨基间苯二酚二盐酸盐（DAR）和对氨基苯甲酸（PABA）。一系列聚（benzobisoxazole-共亚胺）的基础上的3,3'，4,4'-联苯四酸酐（BPDA），4,4'-二氨基二苯醚（ODA）（PBOI）纤维和PBOA制造了通过两步湿纺方法。详细描述了PBOA，并描述了聚合物主链中单体对纤维微结构和性能的影响。2D广角X射线衍射表明，在BPDA-ODA聚酰亚胺主链中掺入的PBOA有利于在热拉伸过程中在所得纤维中形成明确的结晶区域，并显着改善拉伸PBOI的结晶度和晶体取向纤维。拉伸的PBOI纤维的小角度X射线散射图表明纤维中存在典型的周期性层状晶体。结果表明，增加PBOA含量会导致较高的长周期（L）和层状厚度（l _C）。当将混合二胺中的PBOA的摩尔含量从10 mol％增加到50 mol％时，抗拉强度和模量达到282％的最大改进。相应地，在氮气中，所得的PBOI纤维在最大降解速率（T _d-max）和玻璃化转变温度（T _g）下的温度分别增加了28和30°C，这使这些新型聚合物纤维成为先进制造过程中的良好增强材料。复合材料。